Sounds interesting. Do you have a source for the mentioned research?
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For Android i know that you can find some FOSS Telegram clients, in github and telegram itself but also on F-Droid (just to name a few: Telegram FOSS, Nekogram X, Forkgram, Catogram).
On desktop on the other hand, i know of only one other FOSS client (that is called: Kotatogram).
Maybe someone knows of some more FOSS desktop clients?
https://docs.bazzite.gg/Installing_and_Managing_Software/Updates_Rollbacks_and_Rebasing/rebase_guide/
This should answer most, if not all of your questions.
It’s important to remember, that you should rebase to the same DE to avoid issues. Although there shouldn’t be any data loss when rebasing, a backup of your files is recommended.
Edit: Forgot to write, that these principles apply to all atomic distros. But depending on the distro you’re using, the rebasing commands might be slightly different. So always look on the documentation of your distro.